The earth is currently experiencing the Holocene, the period of 11,700 years following the last major ice age. Some in the climate science community have begun referring to the most recent years of this period as the Anthropocene, suggesting that human activity is responsible for much of the change which has occurred since the Industrial Revolution, or since the Little Ice Age.
NASA has recently published a study suggesting that errors in observational data in the early years of the instrumental temperature record caused approximately 20% of the global warming which has occurred over that period to be “missed” due to quirks in the measurements. They have concluded that it is necessary to “adjust” the observations to correct these Quirks; and, that these “adjustments” bring the observations more in line with the scenarios produced by the climate models. These “adjustments” are in addition to the adjustments which had already been made by NCEI, NASA and Hadley Center/UEA CRU in the process of constructing the temperature anomaly products, both currently and retrospectively. The combination of all of these “adjustments” led one wag to rename this period the “Adjustocene”.
Two quotations regarding this issue bear repeating here, one serious and the other in jest:
--“It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong.” Richard P. Feynman
--“95% of Climate Models Agree: The Observations Must Be Wrong.” Roy Spencer
NASA’s recent study seems to suggest that NASA has ignored Feynman and taken Spencer seriously.
Fundamentally, the temperature data are not “adjusted” because of their superb quality, accuracy or precision. Rather, they are adjusted because they lack those attributes. However, once adjusted, they are merely estimates of what the data might have been, had they been collected timely from properly selected, calibrated, sited, installed and maintained instruments. What the climate science community prefers to refer to as “datasets” are therefore, in fact, estimate sets. The climate science community acknowledges that the data are inaccurate, but insists that the estimates are both accurate and precise.